Bonjour qui pourrait m aider s'il vous plaît à l exo juste 48 , 50, 54 merci ❤️❤️

Bonsoir,

48) 
a) - 5/14 - 3/7
= - 5/14 - (3 x 2) / (7 x 2)
= - 5/14 - 6/14
= - 11/14

b) 2/9 - 5/27
= (2 x 3) / (9 x 3) - 5/27
= 6/27 - 5/27
= 1/27

c) - 3/20 - 2/5
= - 3/20 - (2 x 4) / (5 x 4)
= - 3/20 - 8/20
= - 11/20

50)
1) Multiples de 6 : 6 ; 12 ; 18 ; 24 ; 30
Multiples de 8 : 8 ; 16 ; 24 ; 32 ; 40 

2) 
a) 7/6 - 9/8
= (7 x 4) / (6 x 4) - (9 x 3) / (8 x 3)
= 28/24 - 27/24
= 1/24

b) - 1/8 + - 5/6 = - 1/8 - 5/6
= (- 1 x 3) / (8 x 3) - (5 x 4) / (6 x 4)
= - 3/24 - 20/24
= - 23/24

54)
a) 2/7 + 4/9
= (2 x 9) / (7 x 9) + (4 x 7) / (9 x 7)
= 18/63 + 28/63
= 46/63

b) 3/8 - 5/3
= (3 x 3) / (8 x 3) - (5 x 8) / (3 x 8)
= 9/24 - 40/24
= - 31/24

c) - 4/5 - 7/9
= (- 4 x 9) / (5 x 9) - (7 x 5) / (9 x 5)
= - 36/45 - 35/45
= - 71/45

d) 1 + 2/9
= (1 x 9 ) / (1 x 9) + 2/9
= 9/9 + 2/9
 = 11/ 9

e) 1 - 7/3
= (1 x 3) / (1 x 3) - 7/3
= 3/3 - 7/3
= - 4/3

f) 3 + 3/4
= (3 x 4) / (1 x 4) + 3/4
= 12/4 + 3/4
= 15/4